1. Field of the Invention
For the transmission of data between a stationary and a rotating component it is known to convert digital electrical signals into light signals, to transmit these light signals subsequently by a projector (sender) onto a receiver where the received light signals are then reconverted into digital electrical signals. The projector or the receiver in this connection can be correlated with the stationary or the rotating component, respectively.
2. Description of the Related Art
The known contactless data transmission proves to be still satisfactory when only a minimal data rate is to be transmitted and, moreover, the relative speed between the stationary and the rotating component is not very high. Problems result, however, when greater data rates are to be transmitted at a higher relative speed. The reason for this is the fact that a transmission of data is possible only when the projector and the receiver are on the same optical axis. However, this is the case only once for each revolution. Moreover, difficulties with respect to the continuity of the data transmission result in this connection.
The solution to this object according to the invention resides in that between the projector and the receiver an annular light guide body of a transparent material with integrated reflection prisms is integrated and the exit surface of the light guide body opposite the receiver has a matte finish.
The invention uses in this connection the known effect that light which impinges on the surface of a glass body or a glass-like body can be propagated in this body by total reflection. When then also reflection prisms are provided on the body such that the critical angle of total reflection is surpassed, each of the light beams guided through the body exits refractedly at the interface glass/air, referred to as free surface. If, moreover, the exit surface has a matt finish, the light will exit in a diffuse way so that the free surface irradiates.
The invention now employs an annular light guide body of a transparent material such as glass or plastic. With the directed arrangement of reflection prisms on the light guide body, each light beam introduced into the light guide body is totally reflected up to the matt finish exit surface (free surface) where the light beam then exits diffusely. The receiver opposite this free surface can thus receive the light directly and guide it farther in a directed way to the electronic evaluation device. Independent of whether the light guide body rotates relative to the receiver or the receiver rotates relative to the light guide body, the receiver at any time can receive the light signal emitted by the projector and can guide it farther.
The invention thus makes it possible to guide the light signals emitted by the projector continuously via the light guide body to a receiver, independent of the position of the receiver and light guide body relative to one another. In this way, in comparison to the prior art, a considerably increased data rate can be transmitted in a contactless way with significantly higher relative speed between the stationary and the rotating component.
In the context of the invention the light signals are transmitted only in one direction, i.e., either from the stationary to the rotating component or from the rotating to the stationary component. If a bidirectional signal transmission is desired, two arrangements that are independent from one another are required.
A further advantage of the invention resides in that, due to the annular configuration of the light guide body, its free central area can be used for receiving components such as, for example, axles and shafts. Moreover, it is feasible that cables or lines for the transport of any type of product can be arranged within this central area.
The light guide body according to the invention is easily manufactured, for example, by injection molding of acrylic glass. In this way, light guide bodies can be produced economically and especially precisely reproducibly in almost any desired size and in high numbers.
An especial advantageous embodiment of the invention is seen in the features of claim 2. In accordance therewith, the projector comprises at least one laser diode which is pulsable according to the rhythm of digital electrical signals and the receiver comprises at least one photo transistor coupled directly or indirectly with an electronic evaluation device. Accordingly, it is possible to integrate almost any number of laser diodes, with different wavelengths and with receivers appropriately adjusted thereto, into the arrangement. Thus, it is possible to contactlessly transmit simultaneously light signals that are independent from one another between a stationary and a rotating component via the light guide body.
In this context, according to claim 3 it is then advantageous that each of the photo transistors has a filter, adjusted to a certain wavelength, especially in a bandwidth range of approximately 2 nanometer (nm), correlated therewith.
Since in the context of the invention a light beam introduced into the light guide body is divided by the annular configuration of the light guide body and passes through it in two directions, the two light beams, aside from the ideal 180xc2x0 position of the projector and the receiver, always travel two different distances. The receiver must therefore evaluate two light signals which are staggered temporally relative to one another. In the case of great data rates and high relative speeds, this can result in that the precision of the data transmission is less than desirable. In order to ensure also in these situations a qualitatively absolutely satisfactory data transmission, the invention suggests according to the features of claim 4 that the projector has a collimator as well as a light guide array comprising several light guides of identical length, wherein the light guides are connected with identical spacing circumferentially to the light guide body in a light-conducting way. The number of light guides depends in this connection substantially on the data rate, the relative speed of the stationary to the rotating component, the desired transmission quality as well as the size of the light guide body being used. Light guides of identical length as well as the uniformly staggered circumferential arrangement of the connections of the light guides to the light guide body ensure that each light beam must travel only short distances in the light guide body. The result is a very minimal propagation delay of the respective light signal in combination with a considerably greater receiving precision. The data rate can be extremely high while providing a great relative speed of the rotating to the stationary component.
A further perfection of the inventive arrangement is provided by the features of claim 5. Accordingly, the light guides correlated with a laser diode by means of the light guide array are connected to shells which are connected with the annular light guide body to form a unitary part. Moreover, reflection prisms are provided on the light guide body which are correlated with the individual shells and are accordingly configured in a segmented and shell-like fashion. This configuration ensures that the light signal introduced via a light guide into each shell will enter only the segment of the light guide body correlated with this shell. A circular propagation of the light in the light guide body is reliably prevented.
Due to the segmented configuration of the reflection prisms it could be possible that gaps result between neighboring segments which would cause disruptions. These gaps are prevented according to claim 5 in that the reflection prisms, which, in comparison to the light guide body, have deviating curvatures, penetrate one another at the interfaces of the shells and the light guide body. This results in overlap of the light spots at the interfaces so that no temporal displacements and also no propagation delays of the light signals will result because of the simultaneous phase-identical introduction of the light into the shells.